Leonardo DiCaprio is known for many things: as one of the best actors of our times, as a lover of beautiful ladies, and as a strong champion for planet Earth. Sure, he is human and has his vices, but DiCaprio has been a fervent supporter of environmental and animal conservation efforts throughout most of his career. This week, Leonardo DiCaprio joined forces with Mark Ruffalo as they launched 100%, "a campaign aimed at making energy from renewable sources available to everyone," according to the Associated Press.

Ruffalo spoke to supporters at the event, saying, “This is really mankind’s greatest threat, and it should take some serious problem solving on all of our parts, and we don’t really have to give up anything to do it ... We will be collecting the sun and the wind that falls on us every single day.”

It really is a beautiful thing to see two Hollywood celebrities use their platform for a cause that is equal in importance to every living being on this planet. In fact, there are a few stars who have done the same. Click through for some of Hollywood's most eco-friendly celebrities.

Jessica Alba

Jessica Alba might be one of the biggest celebrity business success stories. She has built a billion dollar company in The Honest Company, which only stocks products that are non-toxic and support ethical and sustainable consumerism.

Penelope Cruz

Penelope Cruz lent her support to Conservation International’s Nature is Speakinginitiative, which released a series of short films that show that the Earth doesn’t need us, but we need her. She narrated the part of “water,” and joined other A-list celebs. She has also worked to encourage fellow celebs to use eco-friendly hybrid cars as transportations to red carpet events.

Cate Blanchett

In 2011, Blanchett launched a project in her native Sydney, Australia that would be the world’s largest rainwater harvesting system. After supporting a carbon tax to limit gas emissions, she explained, ”Everyone will benefit if we protect the environment. There is a societal cost of increased pollution and that’s what I’m passionate about as a mother. That’s where it gets me in the gut. I can’t look my children in the face if I’m not trying to do something in my small way and to urge other people," according to her website.

Jared Leto

Jared Leto has committed to a life of veganism. He and his band, 30 Seconds to Mars, filmed a video for their song “A Beautiful Lie” to bring attention to global warming. The video was filmed over the Arctic Circle and featured facts about climate change. Leto said at the time, “We all know by now that our planet is in deep trouble. We have abused it horribly and we are paying the price. It’s time to try to do what we can, both as individuals and collectively, to find better and kinder ways to live. It’s not our right; it’s our responsibility. We are all guilty. We can all change,”

Natalie Portman

Portman is mostly known for being a very big supporter of living cruelty-free, especially in keeping a vegan diet. In addition, she partnered with fashion brand Te Casan to create a line of vegan footwear, the proceeds from which were donated to The Nature Conservancy. She also took part in an Animal Planet documentary, Gorillas on the Brink, in which she traveled to Rwanda to highlight the threats to the gorilla population caused by humans.